BLACK DIAMOND, Alta. — The Transportation Safety Board says pilots of a tow plane and a glider couldn't see each other before they collided mid-air southwest of Calgary last year.
Neither the weather nor sun position were believed to be factors in the crash near Black Diamond, Alta., last July 26.
Instructor Allan Wood, 68, and student Adam Leinweber, 18, who were inside the glider died at the scene.
The plane that had been towing them was severely damaged, but the pilot of that aircraft was uninjured and managed to land successfully.
The federal safety agency says the Cu Nim Gliding Club had no standard procedure for what to do if a tow plane pilot loses sight of a glider once it's released.
The board also says that while both aircraft had on-air collision avoidance systems, the one on the tow plane wasn't working the day of the crash.
"Neither pilot saw the other aircraft in time to avoid a mid-air collision, partly owing to the inherent limitations of the see-and-avoid principle," the safety board said in its report released Monday.
"Relying solely on visual detection increases the risk of collision while in uncontrolled airspace. Pilots are encouraged to broadcast their intentions to maintain the situational awareness of other aircraft ... if an aircraft is equipped with an (airborne collision avoidance system), it is important that the system be maintained in a serviceable condition."
The board said usually a glider will release from the plane that's towing it when both are flying straight and level. In this case, the glider released from the tow line halfway through a turn and sooner than expected. The pilot was unaware of the release.
The collision happened 34 seconds later.
The glider's vertical and horizontal stabilizers separated when it collided with the tow plane. The glider entered a dive from which it could not recover and struck the ground almost vertically.
This report by The Canadian Press was first published Feb. 10, 2020
The Canadian Press
With files from Okotoks Today